For discussion of all the other girl+mecha lines that have cropped up since Shinki began: Frame Arms: Girls, Megami Device, Armor Girls Project, Desktop Army, etc. This includes kinda-sortas like Daibadi's Polynian and things like Strike Witches and Fumikane's original Mecha Musume.

I'd think a Blade Liger would be the first...
It's a shame that Figuttos are 1/10 while the other mecha musume we're seeing lately are 1/12.
I have a dream that one day little Busou Shinkis and COMPOSITE Haruhis will be able to join hands with little Gundam Girls and Zoids Girls as sisters and brothers in arms.